/**
 * @file buffer_utils.c
 * @brief 通用缓冲区处理工具实现
 * @details 本文件实现了通用的缓冲区处理工具功能，包括字节序转换（大端序/小端序）、
 *          安全的缓冲区读写操作、缓冲区操作（复制、移动、比较、设置）、校验和计算等。
 *          提供完整的缓冲区管理接口，确保数据操作的安全性和可靠性。
 * 
 * @author zyb
 * @date 2025-09-25
 * @version 1.0
 * 
 * @note 所有缓冲区操作都包含边界检查，防止缓冲区溢出
 * @warning 字节序转换函数需要根据目标平台选择合适的实现
 * 
 * @see buffer_utils.h
 */

#include "buffer_utils.h"
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

/* ==================== 字节序转换函数实现 ==================== */

/**
 * @brief 16位主机序转网络序
 */
uint16_t htons_16(uint16_t value) {
    return ((value & 0xFF) << 8) | ((value >> 8) & 0xFF);
}

/**
 * @brief 16位网络序转主机序
 */
uint16_t ntohs_16(uint16_t value) {
    return htons_16(value); /* 网络序转主机序与主机序转网络序相同 */
}

/**
 * @brief 32位主机序转网络序
 */
uint32_t htonl_32(uint32_t value) {
    return ((value & 0xFF) << 24) | 
           (((value >> 8) & 0xFF) << 16) | 
           (((value >> 16) & 0xFF) << 8) | 
           ((value >> 24) & 0xFF);
}

/**
 * @brief 32位网络序转主机序
 */
uint32_t ntohl_32(uint32_t value) {
    return htonl_32(value); /* 网络序转主机序与主机序转网络序相同 */
}

/**
 * @brief 64位主机序转网络序
 */
uint64_t htonll_64(uint64_t value) {
    return ((uint64_t)htonl_32((uint32_t)(value & 0xFFFFFFFF)) << 32) |
           htonl_32((uint32_t)(value >> 32));
}

/**
 * @brief 64位网络序转主机序
 */
uint64_t ntohll_64(uint64_t value) {
    return htonll_64(value); /* 网络序转主机序与主机序转网络序相同 */
}

/**
 * @brief 32位浮点数字节序转换
 */
float htonf_32(float value) {
    union { float f; uint32_t i; } u;
    u.f = value;
    u.i = htonl_32(u.i);
    return u.f;
}

float ntohf_32(float value) {
    return htonf_32(value);
}

/**
 * @brief 64位浮点数字节序转换
 */
double htond_64(double value) {
    union { double d; uint64_t i; } u;
    u.d = value;
    u.i = htonll_64(u.i);
    return u.d;
}

double ntohd_64(double value) {
    return htond_64(value);
}

/* ==================== 缓冲区读写函数实现 ==================== */

/**
 * @brief 安全读取8位数据
 */
buffer_error_t buffer_read_u8(const uint8_t* buffer, size_t offset, uint8_t* value) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    if (value == NULL) {
        return BUFFER_ERROR_NULL_POINTER;
    }
    
    *value = buffer[offset];
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全读取16位数据
 */
buffer_error_t buffer_read_u16(const uint8_t* buffer, size_t offset, uint16_t* value, int big_endian) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    if (value == NULL) {
        return BUFFER_ERROR_NULL_POINTER;
    }
    
    uint16_t raw_value = *(uint16_t*)(buffer + offset);
    *value = big_endian ? ntohs_16(raw_value) : raw_value;
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全读取32位数据
 */
buffer_error_t buffer_read_u32(const uint8_t* buffer, size_t offset, uint32_t* value, int big_endian) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    if (value == NULL) {
        return BUFFER_ERROR_NULL_POINTER;
    }
    
    uint32_t raw_value = *(uint32_t*)(buffer + offset);
    *value = big_endian ? ntohl_32(raw_value) : raw_value;
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全读取64位数据
 */
buffer_error_t buffer_read_u64(const uint8_t* buffer, size_t offset, uint64_t* value, int big_endian) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    if (value == NULL) {
        return BUFFER_ERROR_NULL_POINTER;
    }
    
    uint64_t raw_value = *(uint64_t*)(buffer + offset);
    *value = big_endian ? ntohll_64(raw_value) : raw_value;
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全写入8位数据
 */
buffer_error_t buffer_write_u8(uint8_t* buffer, size_t offset, uint8_t value) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    
    buffer[offset] = value;
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全写入16位数据
 */
buffer_error_t buffer_write_u16(uint8_t* buffer, size_t offset, uint16_t value, int big_endian) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    
    uint16_t write_value = big_endian ? htons_16(value) : value;
    *(uint16_t*)(buffer + offset) = write_value;
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全写入32位数据
 */
buffer_error_t buffer_write_u32(uint8_t* buffer, size_t offset, uint32_t value, int big_endian) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    
    uint32_t write_value = big_endian ? htonl_32(value) : value;
    *(uint32_t*)(buffer + offset) = write_value;
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全写入64位数据
 */
buffer_error_t buffer_write_u64(uint8_t* buffer, size_t offset, uint64_t value, int big_endian) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    
    uint64_t write_value = big_endian ? htonll_64(value) : value;
    *(uint64_t*)(buffer + offset) = write_value;
    return BUFFER_SUCCESS;
}

/* ==================== 缓冲区操作函数实现 ==================== */

/**
 * @brief 安全复制缓冲区数据
 */
buffer_error_t buffer_copy(uint8_t* dest, const uint8_t* src, size_t size) {
    buffer_error_t ret = buffer_validate_pointer(dest);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    ret = buffer_validate_pointer(src);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    
    memcpy(dest, src, size);
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全设置缓冲区数据
 */
buffer_error_t buffer_set(uint8_t* buffer, uint8_t value, size_t size) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    
    memset(buffer, value, size);
    return BUFFER_SUCCESS;
}

/**
 * @brief 计算缓冲区校验和
 */
uint8_t buffer_checksum(const uint8_t* buffer, size_t size) {
    if (buffer_validate_pointer(buffer) != BUFFER_SUCCESS) {
        return 0;
    }
    
    uint8_t checksum = 0;
    for (size_t i = 0; i < size; i++) {
        checksum += buffer[i];
    }
    return checksum;
}

/**
 * @brief 计算缓冲区CRC16校验
 */
uint16_t buffer_crc16(const uint8_t* buffer, size_t size) {
    if (buffer_validate_pointer(buffer) != BUFFER_SUCCESS) {
        return 0;
    }
    
    uint16_t crc = 0xFFFF;
    for (size_t i = 0; i < size; i++) {
        crc ^= buffer[i];
        for (int j = 0; j < 8; j++) {
            if (crc & 1) {
                crc = (crc >> 1) ^ 0xA001;
            } else {
                crc >>= 1;
            }
        }
    }
    return crc;
}

/**
 * @brief 计算缓冲区CRC32校验
 */
uint32_t buffer_crc32(const uint8_t* buffer, size_t size) {
    if (buffer_validate_pointer(buffer) != BUFFER_SUCCESS) {
        return 0;
    }
    
    static const uint32_t crc32_table[256] = {
        0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, 0x706AF48F,
        0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
        0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91, 0x1DB71064, 0x6AB020F2,
        0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
        0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
        0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
        0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B, 0x35B5A8FA, 0x42B2986C,
        0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
        0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423,
        0xCFBA9599, 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
        0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190, 0x01DB7106,
        0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
        0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D,
        0x91646C97, 0xE6635C01, 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
        0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
        0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
        0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7,
        0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
        0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA,
        0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
        0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81,
        0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
        0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683, 0xE3630B12, 0x94643B84,
        0x0D6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
        0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
        0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
        0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5, 0xD6D6A3E8, 0xA1D1937E,
        0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
        0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55,
        0x316E8EEF, 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
        0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE, 0xB2BD0B28,
        0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
        0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A, 0x9C0906A9, 0xEB0E363F,
        0x72076785, 0x05005713, 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
        0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
        0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
        0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69,
        0x616BFFD3, 0x166CCF45, 0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
        0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC,
        0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
        0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693,
        0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
        0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
    };
    
    uint32_t crc = 0xFFFFFFFF;
    for (size_t i = 0; i < size; i++) {
        crc = crc32_table[(crc ^ buffer[i]) & 0xFF] ^ (crc >> 8);
    }
    return crc ^ 0xFFFFFFFF;
}

/* ==================== 缓冲区验证函数实现 ==================== */

/**
 * @brief 验证缓冲区边界
 */
buffer_error_t buffer_validate_bounds(const uint8_t* buffer, size_t offset, size_t size, size_t buffer_size) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    
    if (offset + size > buffer_size) {
        return BUFFER_ERROR_OUT_OF_BOUNDS;
    }
    
    return BUFFER_SUCCESS;
}

/**
 * @brief 验证缓冲区指针
 */
buffer_error_t buffer_validate_pointer(const uint8_t* buffer) {
    return (buffer != NULL) ? BUFFER_SUCCESS : BUFFER_ERROR_NULL_POINTER;
}

/* ==================== 浮点数读写函数实现 ==================== */

/**
 * @brief 安全读取32位浮点数
 */
buffer_error_t buffer_read_f32(const uint8_t* buffer, size_t offset, float* value, int big_endian) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    if (value == NULL) {
        return BUFFER_ERROR_NULL_POINTER;
    }
    
    float raw_value = *(float*)(buffer + offset);
    *value = big_endian ? ntohf_32(raw_value) : raw_value;
    return BUFFER_SUCCESS;
}

/**
 * @brief 安全写入32位浮点数
 */
buffer_error_t buffer_write_f32(uint8_t* buffer, size_t offset, float value, int big_endian) {
    buffer_error_t ret = buffer_validate_pointer(buffer);
    if (ret != BUFFER_SUCCESS) {
        return ret;
    }
    
    float write_value = big_endian ? htonf_32(value) : value;
    *(float*)(buffer + offset) = write_value;
    return BUFFER_SUCCESS;
}
